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@@ -4,16 +4,25 @@ Kernel booting process. Part 2.
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First steps in the kernel setup
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-We started to dive into linux kernel internals in the previous [part](linux-bootstrap-1.md) and saw the initial part of the kernel setup code. We stopped at the first call of the `main` function (which is the first function written in C) from [arch/x86/boot/main.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c). Here we will continue to research the kernel setup code and see what `protected mode` is, some preparation for the transition into it, the heap and console initialization, memory detection and much much more. So, Let's go ahead.
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+We started to dive into linux kernel internals in the previous [part](linux-bootstrap-1.md) and saw the initial part of the kernel setup code. We stopped at the first call to the `main` function (which is the first function written in C) from [arch/x86/boot/main.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c).
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+
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+In this part we will continue to research the kernel setup code and
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+* see what `protected mode` is,
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+* some preparation for the transition into it,
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+* the heap and console initialization,
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+* memory detection, cpu validation, keyboard initialization
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+* and much much more.
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+
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+So, Let's go ahead.
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Protected mode
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-Before we can move to the native Intel64 [Long mode](http://en.wikipedia.org/wiki/Long_mode), the kernel must switch the CPU into protected mode.
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+Before we can move to the native Intel64 [Long Mode](http://en.wikipedia.org/wiki/Long_mode), the kernel must switch the CPU into protected mode.
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What is [protected mode](https://en.wikipedia.org/wiki/Protected_mode)? Protected mode was first added to the x86 architecture in 1982 and was the main mode of Intel processors from the [80286](http://en.wikipedia.org/wiki/Intel_80286) processor until Intel 64 and long mode came. The Main reason to move away from [real mode](http://wiki.osdev.org/Real_Mode) is that there is very limited access to the RAM. As you may remember from the previous part, there is only 2^20 bytes or 1 megabyte, sometimes even only 640 kilobytes of RAM available in real mode.
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-Protected mode brought many changes, but the main one is the difference memory management. The 24-bit address bus was replaced with a 32-bit address bus. It allows access to 4 gigabytes of physical address space vs 1MB of real mode. Also [paging](http://en.wikipedia.org/wiki/Paging) support was added, which you can read about in the next sections.
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+Protected mode brought many changes, but the main one is the difference in memory management. The 20-bit address bus was replaced with a 32-bit address bus. It allows access to 4-gigabytes of physical address space vs 1MB of real mode. Also [paging](http://en.wikipedia.org/wiki/Paging) support was added, which you can read about in the next sections.
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Memory management in protected mode is divided into two, almost independent parts:
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kittyhawk